Cleaning cassette
BACKGROUND OF THE INVENTION 
     The present invention provides an apparatus for cleaning the record/playback head of a cassette drive device such as a magnetic tape drive device, the apparatus having a casing in the form of a cassette which may be inserted into the cassette drive device. 
     The invention is particularly concerned with streamer tape drives, as used for back-up purposes in computer installations. U.S. Pat. No. 4,631,614 discloses in FIG. 6 a cleaner for the heads of a streamer tape drive in which a complex drive train transmits drive to a rocking cleaning head which wipes a pad across the heads in a direction transverse to the direction of tape movement (or the longitudinal extent of the tape). Other head cleaning proposals include European Patent Application No. 0 188 655 which is a purely manual streamer tape drive head cleaning system, and U.S. Pat. Nos. 4,442,468; 4,149,206 and 3,955,214 which describe cleaners for audio tape cassette drives of well-known type in which a cleaning means is driven from the usual sprocket or hub of the cassette. We have found that none of these systems are satisfactory for streamer tape drives in providing sufficient cleaning action without causing undue wear on the heads. 
     SUMMARY OF THE INVENTION 
     The present invention is defined in the appended claims to which reference should now be made for a definition thereof. 
     A particularly preferred example of the invention takes the form of a cleaning cassette having a casing and containing a wiper arm pivoted in the casing at one end and at the other end carrying a replaceable wiper pad assembly which follows an arcuate path on pivotal movement of the wiper arm. The wiper arm is driven from the capstan drive wheel of the drive the heads of which are being cleaned through a pick-up wheel which contacts the capstan drive wheel when the cleaning cassette is in use. The pick-up wheel drives a large wheel through toothed gearing and a crank arm is eccentrically pivoted by one end on the large wheel. The other end of the crank arm is attached to the wiper arm to drive the same. 
     The replaceable wiper pad assembly is slidable into a T-socket on the wiper arm and includes a pad having a thicker central portion and opposed thinner planar wings. A metal base plate is crimped over the wings. 
     It is an advantage of the head cleaning cassette of the present invention that it can be loaded into a magnetic tape drive device in the same way as a magnetic tape cassette is loaded. A further advantage is that the cassette is operated by the tape drive to simply and effectively clean the head. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Cleaning cassettes embodying the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic plan view of a cleaning cassette in accordance with this invention; 
     FIG. 2 is a sectional view taken on the line II--II in FIG. 1 showing the gear drive; 
     FIG. 3 is a sectional view taken on the line III--III in FIG. 1 showing the wiper arm; 
     FIG. 4 is a view of the wiper head; 
     FIG. 5 shows the wiper head in a partially-assembled condition; 
     FIG. 6 is a view similar to FIG. 4 of a possible modification of the wiper head; 
     FIG. 7 is a detail view showing a capstan cleaning pad; 
     FIG 8 is a section taken on line VIII--VIII in FIG. 7; and 
     FIG. 9 is a view similar to FIG. 1 of a slightly modified head cleaning cassette. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIGS. 1 to 3, the cleaning cassette 10 has a casing 12 designed to be suitable for loading into a magnetic tape drive device or &#34;streamer&#34; tape such as commonly used for back-up purposes in computer installations. As the external shape of the casing 12 is of standard type, it is not described here in detail; it will be seen that it has a thickness substantially less than its width and length to present a generally planar configuration. A typical size is approximately 150 mm by 100 mm by 16 mm. The casing houses a wiper arm 14 movable in the plane of the casing about a pivot 16 formed on the casing. The head end remote from the pivot 16 is formed with a T-slot 18 to receive a wiper pad, as described below. 
     To provide drive to the wiper arm, a pick-up wheel 20 frictionally engages with the capstan drive wheel (not shown) of a cassette tape drive in conventional manner. The pick-up wheel 20 is mounted coaxially with a first toothed gear 22 which engages an idler gear 24 which in turn engages a larger gear 26. The large gear 26 operates as a cam wheel and to that end has an eccentric bush boss or 28 on its upper surface over which is mounted a crank arm 30 with a corresponding aperture 32 at one end. The crank arm 30 is linked to the middle portion of the wiper arm at its other end by a rivet portion 34. 
     In use, the cassette is loaded into a magnetic tape drive device in the normal way. When the tape drive is started, the capstan drive wheel drives the pick-up wheel 20 which rotates the cam wheel 26 through the gear train 22,24. The gear train provides a reduction of between 2:1 and 10:1, preferably around 5:1. The rotation of the cam wheel 26 then causes the crank arm 30 to reciprocate the wiper arm 14 so that the head end of the wiper arm carrying the wiper pad moves back and forth across the head to be cleaned, generally in the direction of tape movement, namely as shown by the double headed arrow A. 
     The toothed gear drive could be replaced by a frictional drive coupling as an alternative. 
     The arcuate path for the cleaning head has the advantage that maximum cleaning pressure is applied to clean the drive head over its central region where the build-up of dirt may be greatest. This we have found to be particularly effective in removing contaminant while tending to minimise wear on the heads. The cassette illustrated thus provides a self-contained automatic head cleaning apparatus in a simple and compact form. Provision may be made in the casing for the introduction of a cleaning solvent to improve the cleaning efficiency of the pad(s). 
     It should be noted that the cassette is simple to make and that the bushings and mountings for the various components are made by appropriate shaping of the base and top plates as shown. 
     The cleaning pad assembly will now be described with reference to FIGS. 4 and 5. The pad assembly comprises a pre-formed foam element 40 and an aluminum strip 42. As shown in FIG. 5, the preshaped foam elements has a solid thicker central portion 44 and two thinner wings 46. The aluminium strip forms a base for the pad and has two flanges 48 which are folded over to compress the wings 46 and thereby secure the foam element 40. The aluminium base can then be slid only the T-slot 18 at the top of the wiper arm 14. The pad is thus easily replaceable when it becomes soiled. In a modification of the head 18 as shown in FIG. 6, the head is curved and receives a correspondingly curved pad assembly. 
     The foam pad 40 is shaped so that as it passes across the head it can distort sideways as shown by the dashed lines B in FIG. 4. This we have found to be particularly effective in achieving good cleaning without undue wear on the heads, especially when considered together with the arcuate path transversed by the pad. 
     Other advantageous features may be added to the cassette described above. For example, it may be desirable to include in the casing a static pad arranged to come into contact with the capstan drive wheel so as to provide a cleaning action as the capstan rotates. Such a static foam pad 50 is shown in FIG. 7 and 8 and is mounted in a moulding 52 in the casing so as to project against the surface of the capstan drive wheel 54. The pad 50 is held in a U-shaped aluminum strip retained in a slot 56 in the moulding 52. 
     The modification of FIG. 9 is similar in principle to the cleaner of FIG. 1 and will not therefore be described again in detail. In this case however the idler gear 24 is omitted. The pick-up wheel 60 is larger than the pick-up wheel 20 and frictionally engages with the capstan drive wheel. The pick-up wheel 60 is mounted coaxially with a toothed gear 62 which engages directly with the gear 26. As with FIG. 1, rotation of the pick-up wheel is converted to arcuate reciprocation of the wiper pad 40 against the head 64 to be cleaned, the reciprocation being in the direction parallel to the direction of movement of the tape in a standard cassette. The overall size of the casing 12 in this case is approximately 80 mm by 60 mm. 
     Certain drives have photocell/lamp combinations to detect the beginning and end of tape of a standard cassette. It may be necessary to include one or more opaquing plates 68 in the cleaning cassette located to interrupt the light from the lamp so that it does not reach the photocell. Otherwise the tape drive may switch off automatically, as it apparently senses that the end of tape has been reached. 
     Many modifications may be made to the arrangements illustrated within the scope of the invention as defined in the following claims.